python - 如何模拟对象方法返回值

Question

我目前拥有的是:

def some_method():
    some_obj = some_other_method()
    # This is what I want to mock return value of:
    some_obj.some_obj_some_method()

@patch('some_package.some_other_method')
def test_some_stuff(some_other_method_patch):
    some_other_method_patch.return_value = SomeObject()

我怎样才能将 some_obj.some_obj_some_method() 的返回值设置为 False？

Answer 1

patch('some_package.some_other_method') 会将函数 some_other_method 替换为 Mock。现在您需要替换此模拟的方法 some_obj_some_method 的返回值:

mock.return_value.some_obj_some_method.return_value = False

完整示例:

# some_package.py

class SomeObject:
    def some_obj_some_method(self):
        raise RuntimeError()


def some_other_method():
    return SomeObject()


def some_method():
    some_obj = some_other_method()
    # This is what you want to mock return value of:
    return some_obj.some_obj_some_method()

测试:

from unittest.mock import patch
from some_package import SomeObject, some_method

@patch('some_package.some_other_method')
def test_some_stuff(function_mock):
    function_mock.return_value.some_obj_some_method.return_value = False
    assert not some_method()

测试将按原样通过，将在没有修补的情况下引发 RuntimeError 并且在没有行 function_mock.return_value.some_obj_some_method.return_value = False 的情况下断言失败，因为 some_method 只会返回一个 Mock，它永远不会是 False。